Dongrong Fm
Type Locality and Naming
It was named by Huang Guanjun in 1983. The naming section is located in the area of Dongrong, Jixian County, Heilongjiang Province, with the formation being found to occur in the No. 23 drilling well on the No. 15 prospecting profile, No. 97 and 44 drilling wells on the No. 23 prospecting profile, and the No. 312 drilling well on the No. 27 prospecting profile, with its reference section being situated in the Suibin area found in No. 10 drilling well on the No. 4 prospecting profile (the well site is about 47°25′ N and 131°12′ E).
Synonym: （东荣组）
Lithology and Thickness
Lower part is composed essentially of dark-grey and grey-black siltstones, intercalated with tuff. Upper part is grey-white and grey-green fine-grained sandstones, intercalated with thin-bedded tuff, with a maximum thickness of about 395 m.
Relationships and Distribution
Lower contact
In the Suibin area, its basal part together with the underlying Suibin Fm represents continuous deposits. In the Jixian area it directly overlies the old strata there.
Upper contact
No information given. Regionally, the next younger unit might be the Baoquanling Fm (Eocene), or perhaps the Didao Fm (mid-Cret; column Cret 22, which is slightly to the southeast)?
Regional extent
This formation is distributed mainly in the Suibin and Jixian areas, with a consistent lithology, and a thickness varying in a range of tens of meters to about 200 m.
GeoJSON
Fossils
It yields abundant bivalves, dinoflagellates and a small amount of ammonites fossils. In the Suibin area the bivalves can be divided in ascending order into the following four Buchia zones: (1) B. concentrica zone; (2) B. tenuistriata zone; (3) B. mosquensis-B. rugosa assemblage zone; and (4) B. fischeriana zone; and the dinoflagellates can be divided into (1) the Gonyaulacysta jurassica acme-zone, and (2) the Amphorula delicata zone.
Age
Depositional setting
This formation belongs to littoral shallow-sea deposits.
Additional Information